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「MCOI-09」MCOI Round 9

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T182489: R52546756
This commit is contained in:
Baoshuo Ren 2021-07-07 15:34:06 +08:00 committed by Baoshuo Ren
parent 6899c72512
commit 3ebdb99d95
Signed by: baoshuo
GPG Key ID: 70F90A673FB1AB68
1 changed files with 29 additions and 0 deletions
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Luogu/contest/45812/T182489/T182489.cpp Normal file
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#include <bits/stdc++.h>
using namespace std;
const int mod = 998244353;
int main() {
int n, k;
cin >> n >> k;
int v = 1, q = 1;
for (int i = 0; i < n - k; i++) {
v = 2ll * v % mod;
}
for (int i = n - k + 1; i <= n; i++) {
v = 1ll * i * v % mod;
}
for (int i = 1; i <= k; i++) {
q = 1ll * i * q % mod;
}
int a = 1, e = mod - 2;
while (e) {
if (e & 1) {
a = 1ll * a * q % mod;
}
q = 1ll * q * q % mod;
e >>= 1;
}
cout << 1ll * v * a % mod << endl;
}